The present invention relates to a method for pressing a book block with a rounded back, as well as to a pressing device as defined and a book production line provided with a device of this type.
For standard book block production, several signatures and/or individual sheets are bound together, for example, wherein each individual signature or sheet contains several pages of a book. Alternatively, individual pages can also be bound directly. For the production of book blocks, the signatures or sheets are initially stacked together until a desired number of pages for a book block have been gathered. The signatures in a book block are placed precisely one on top of another and are bound along the back, to create a joint and flat book block back. The same operational steps are used for an alternative production where individual pages are bound, so that a book block with a flat book back is created.
During a following method step, the rounding operation, the signatures and/or individual sheets are displaced parallel to each other and perpendicular to the book back. In the center portion, the backs of the signatures or folded sheets are thus displaced, relative to each other, and change from the flat book block back to form a rounded book block back. Different rounding methods can also be used besides the previously described rounding principle using rollers, for example the so-called hammer-bar principle.
Methods are furthermore known from European patent documents EP 1872963A2 and EP 0676303B1 for which, following the rounding step, a previously rounded book block that is clamped in along the back area is mechanically compressed using known, bar-type rams as tools.
The replaceable tools used for the known pressing operation, which for the most part are embodied concave and are inserted into a pressing bar, are spaced close together and are replaced to match the rounding of the book block back. The tools are normally replaced manually in a time-consuming and involved process.
However, a book production line used for an industrial production of books requires a fast, automatic setup of each device along the book production line for the changeover to a new order, especially for micro editions or small editions, wherein these are understood to include the so-called on-demand orders and the single-book production orders. This process is hindered whenever manual steps are required for the setup.
A manual process is disclosed in. U.S. Pat. No. 3,280,413A for which a pressing operation is realized with the aid of a massive roller. A book block is initially inserted manually into the machine, with the back pointing downward so that the book block is placed above the roller and aligned with its length. The book block remains in the same position for the operational steps of rounding and pressing and is subsequently removed manually from this position, wherein this process requires the joint operation of rounding and pressing tools.
According to this solution, the book block is clamped-in with rounding devices between two bars. For the rounding of the back, the movements of the bars and the movements of the rounding devices are coordinated. The rounding of the back is determined by scanning the thickness of the inserted book block, as well as with the aid of a manually preset value. The scanning provides a movement curve for the roller used to press the back. The roller alternately passes over the book block clamped into the pressing position, in part multiple times, by moving along a bow-shaped path that is adapted to the back rounding. However, this solution requires an extremely high mechanical expenditure and results in very low productivity because the rounding and pressing operations take place at one and the same location.
Furthermore known are different pressing members which, in particular, are embodied as replaceable tools such as rollers or plates and are either pressed only vertically against the back of the book block, or when using a combined pressing and rounding device by following a scan and sweeping across the back.